The present invention relates to a clutch cover assembly, and particularly, to a clutch cover assembly for clamping a clutch disc between an input plate member and itself.
A clutch cover assembly employed in the clutch of an automobile generally comprises a dish-shaped clutch cover, a pressure plate located within the clutch cover, and a diaphragm spring for impelling the pressure plate toward a clutch disc. When the pressure plate is pressed against the clutch disc, the clutch disc becomes clamped between the pressure plate and, as a typical input member, an engine flywheel, thereby engaging the clutch.
Some conventional clutch discs are composed having a plurality of ridged or corrugated cushioning plates fastened to lateral faces of the disc, and a pair of friction material facing rings bonded to the cushioning plates. Such cushioning plates cushion against shocks of clutch engagement, effecting cushioning characteristics represented In a parabolic, gently-sloping curve.
However, it can be difficult to achieve cushioning of desired characteristics using the aforementioned cushioning plates, since through manufacture the cushioning response of each cushioning plate will vary. Furthermore, high temperatures developing In the clutch disc degrade the cushioning plates, reducing the degree of cushioning. Consequently, it is impracticable to maintain original cushioning characteristics.
The applicant has disclosed a clutch cover assembly in Japanese Utility Model Application No. 91681/1991 wherein the cushioning plates are omitted and a disc spring, i.e., a spring washer, is disposed between the diaphragm spring and the pressure plate instead. Impelling force of the diaphragm spring is transmitted to the pressure plate through the spring washer. Cushioning with this structure exhibits very accurate characteristics, and the spring washer is much less susceptible to the effects of high temperatures in the clutch disc, maintaining longevity of the desirable cushioning characteristics.
Characteristics of the cushioning, however, are such that rigidity therein rises suddenly when a circumferential edge of the spring washer in deformation abuts against the pressure place, generating shock during clutch engagement.